Coating unit and coating method

ABSTRACT

The present invention is a coating unit for applying a coating solution on a substrate, comprising: a container enclosing the substrate; a casing for accommodating the container therein; a supply device for supplying a predetermined gas into the casing; a first exhaust pipe for exhausting an atmosphere inside the container; a second exhaust pipe for exhausting an atmosphere inside the casing; a first adjusting device which is disposed in the first exhaust pipe, for adjusting a flow rate of an atmosphere passing through the first exhaust pipe; and a second adjusting device which is disposed in the second exhaust pipe, for adjusting a flow rate of an atmosphere passing through the second exhaust pipe. According to the present invention, the second exhaust pipe is usable for adjusting the exhaust flow rate to maintain a pressure inside the casing at a positive pressure. This makes it possible to divide, with the use of the first exhaust pipe and the second exhaust pipe, the work which satisfies the conditions of exhausting the atmosphere inside the casing to maintain the pressure inside the casing at the positive pressure relative to an amount of the supplied gas and exhausting the atmosphere inside the container at a predetermined flow rate or higher to prevent the atmosphere inside the container from flowing out of the container. Thereby, the atmospheres inside the casing and the container can be controlled more easily.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coating unit and a coating method fora substrate.

2. Description of the Related Art

In a photolithography process, for example, in semiconductor devicefabrication processes, resist coating treatment for applying a resistsolution on a surface of a substrate, for example, a semiconductor wafer(hereinafter referred to as a ‘wafer’), to form a resist film, exposureprocessing for exposing the wafer in a pattern, developing treatment fordeveloping the wafer after being exposed in the pattern, and so on areperformed to form a predetermined circuit pattern on the wafer.

The above resist coating treatment is usually performed in a resistcoating unit, and for example, a cylindrical cup with an upper partthereof being open is provided inside a casing of the resist coatingunit and a spin chuck for holding the wafer by suction to rotate thewafer is provided inside the cup. The resist coating treatment for thewafer is performed in a manner in which the rotated wafer is suppliedwith the resist solution onto the center thereof, the resist solution onthe wafer is diffused by a centrifugal force which is caused by therotation, and a uniform resist film is formed on the wafer.

Furthermore, atmospheres inside the casing and the cup need to bemaintained at predetermined temperature and humidity when the resistcoating treatment is performed. For this purpose, a supply device forsupplying gas such as air and inert gas to the wafer inside the cup andan exhaust device for exhausting the atmosphere inside the cup from abottom portion of the cup are provided in the resist coating unit.Conventionally, only this exhaust device is provided as an exhaustdevice for exhausting an atmosphere inside the resist coating unit andan amount of the gas supplied by the supply device and an amount of theatmosphere exhausted by the exhaust device are adjusted to maintain aprocessing environment of the resist coating treatment.

However, since film thickness of the resist film varies depending on aflow speed when the above-mentioned gas is supplied, it is necessary tomaintain the flow speed of the gas within a predetermined range and itis also necessary to maintain a pressure inside the casing at a positivepressure in order to prevent impurities from the outside of the casingfrom flowing into the casing while maintaining a flow rate of theabove-mentioned exhausted gas at a certain level or higher in order toprevent impurities produced from the wafer from flowing out of the cup.Therefore, it is very difficult to adjust each of the exhaust flow ratesand the flow rate of the supplied gas with only one exhaust device andthe supply device as described above to satisfy all of the aboveconditions.

SUMMARY OF THE INVENTION

The present invention is made in consideration of the above-describedaspects, and its object is to provide a coating unit and a coatingmethod capable of further facilitating atmosphere control in a casingand a cup.

In order to achieve the above object, a coating unit according to thepresent invention is a coating unit for applying a coating solution on asubstrate, comprising: a container enclosing the substrate; a casing foraccommodating the container therein; a supply device for supplying apredetermined gas into the casing; a first exhaust pipe for exhaustingan atmosphere inside the container; a second exhaust pipe for exhaustingan atmosphere inside the casing; a first adjusting device which isdisposed in the first exhaust pipe, for adjusting a flow rate of anatmosphere passing through the first exhaust pipe; and a secondadjusting device which is disposed in the second exhaust pipe, foradjusting a flow rate of an atmosphere passing through the secondexhaust pipe.

A coating method according to the present invention is a coating methodfor applying a coating solution on a substrate, wherein utilized is acoating unit comprising: a container enclosing the substrate; a casingfor accommodating the container therein; a supply device for supplying apredetermined gas into the casing; a first exhaust pipe for exhaustingan atmosphere inside the container; a second exhaust pipe for exhaustingan atmosphere inside the casing; a first adjusting device which isdisposed in the first exhaust pipe, for adjusting a flow rate of anatmosphere passing through the first exhaust pipe; and a secondadjusting device which is disposed in the second exhaust pipe, foradjusting a flow rate of an atmosphere passing through the secondexhaust pipe, and the coating method comprising the step of adjusting aflow rate of the atmosphere inside the casing which is exhausted fromthe second exhaust pipe to maintain a pressure inside the casing at ahigher level than a pressure outside the casing.

According to the present invention, the second exhaust pipe forexhausting the atmosphere inside the casing is provided separately inaddition to the first exhaust pipe for exhausting the atmosphere insidethe container so that the exhaust flow rate can be adjusted by thesecond exhaust pipe to maintain the pressure inside the casing at apositive pressure. This makes it possible to divide, with the use of thefirst exhaust pipe and the second exhaust pipe, the work which satisfiesthe conditions of exhausting the atmosphere inside the casing tomaintain the pressure inside the casing at the positive pressurerelative to the amount of the supplied gas and exhausting the atmosphereinside the container at a predetermined flow rate or higher to preventthe atmosphere inside the container from flowing out of the container asdescribed above. Consequently, the atmospheres inside the casing and thecontainer can be controlled more easily.

According to the present invention, the use of the second exhaust pipefor maintaining the pressure inside the casing at the positive pressuremakes it possible to have the works of adjusting the exhaust flow rateof the atmosphere inside the container and adjusting the positivepressure inside the casing, which are conventionally carried out by oneexhaust pipe, performed separately by different exhaust pipes tofacilitate each of the adjustments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a schematic structure of a coating anddeveloping treatment system including a resist coating unit according toan embodiment of the present invention;

FIG. 2 is a front view of the coating and developing treatment system inFIG. 1;

FIG. 3 is a rear view of the coating and developing treatment system inFIG. 1;

FIG. 4 is an explanatory view of a vertical cross section of the resistcoating unit;

FIG. 5 is an explanatory view of a horizontal cross section of theresist coating unit in FIG. 4;

FIG. 6 is a plan view of a flow dividing plate used in the resistcoating unit; and

FIG. 7 is an explanatory view of a vertical cross section showinganother structure example of the resist coating unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowto detail the present invention. FIG. 1 is a plan view of a coating anddeveloping treatment system 1 including a coating unit according to thepresent invention, FIG. 2 is a front view of the coating and developingtreatment system 1, and FIG. 3 is a rear view of the coating anddeveloping treatment system 1.

As shown in FIG. 1, the coating and developing treatment system 1 has astructure in which a cassette station 2 for carrying, for example, 25wafers W in a unit of cassette from/to the outside to/from the coatingand developing treatment system 1 and for carrying the wafers W to/froma cassette C, a processing station 3 composed of various kinds ofprocessing units which are disposed in multi-tiers, for performingpredetermined processing for the wafers W one by one in coating anddeveloping processes, and an interface section 4 for delivering thewafers W to/from a not-shown aligner which is disposed adjacent to theprocessing station 3 are integrally connected.

In the cassette station 2, a plurality of the cassettes C are mountablein predetermined positions on a cassette mounting table 5, which servesas a mounting portion, in a line in an X direction (a vertical directionin FIG. 1). Furthermore, a wafer carrier 7, which is movable in thealignment direction of the cassettes (the X direction) and in analignment direction of the wafers W housed in the cassette C (a Zdirection; a perpendicular direction), is provided to be movable along acarrier path 8 so that it is selectively accessible to each of thecassettes C.

The wafer carrier 7 has an alignment function for aligning the wafers W.The wafer carrier 7 is structured so as to be also accessible to anextension unit 32 included in a third processing unit group G3 on aprocessing station 3 side as will be described later.

In the processing station 3, a main carrier 13 is provided in a centerpart thereof, and various kinds of the processing units are multi-tieredon a periphery of the main carrier 13 to constitute a processing unitgroup. In the coating and developing treatment system 1, where fourprocessing unit groups G1, G2, G3 and G4 are provided, the first and thesecond processing unit groups G1 and G2 are disposed on a front side ofthe coating and developing treatment system 1, the third processing unitgroup G3 is disposed adjacent to the cassette station 2, and the fourthprocessing unit group G4 is disposed adjacent to the interface section4. Furthermore, a fifth processing unit group G5 depicted by the brokenline is allowed to be additionally disposed on a rear side as an option.The main carrier 13 is capable of carrying the wafers W to/from variouskinds of later described processing units which are disposed in theseprocessing unit groups G1, G2, G3, and G4. Incidentally, the number andthe arrangement of the processing unit groups vary depending on whichkind of processing is performed on the wafers W and the number of theprocessing unit groups is optionally selective accordingly.

In the first processing unit group G1, for example, as shown in FIG. 2,a resist coating unit 17 serving as a coating unit according to thisembodiment and a developing unit 18 for developing the wafers W afterexposure processing are two-tiered in the order from the bottom.Similarly, in the second processing unit group G2, a resist coating unit19 and a developing unit 20 are two-tiered in the order from the bottom.

In the third processing unit group G3, for example, as shown in FIG. 3,a cooling unit 30 for cooling the wafers W, an adhesion unit 31 forincreasing fixability between a resist solution and the wafers W, theextension unit 32 for keeping the wafers W on standby therein,pre-baking units 33 and 34 for drying a solvent in the resist solution,post-baking units. 35 and 36 for performing heat treatment after thedeveloping treatment, and so on are, for example, seven-tiered in theorder from the bottom.

In the fourth processing unit group G4, for example, a cooling unit 40,an extension and cooling unit 41 for spontaneously cooling the mountedwafers W, an extension unit 42, a cooling unit 43, post-exposure bakingunits 44 and 45 for performing heat treatment after the exposureprocessing, post-baking units 46 and 47, and so on are, for example,eight-tiered in the order from the bottom.

In a center part of the interface section 4, a wafer carrier 50 isprovided. The wafer carrier 50 is structured so as to be movable in theX direction (the vertical direction in FIG. 1) and the Z direction (theperpendicular direction), and to be rotatable in a θ direction (arotational direction about an axis Z), so that it is accessible to theextension and cooling unit 41 and the extension unit 42 which areincluded in the fourth processing. unit group G4, a peripheral aligner51, and the not-shown aligner to carry the wafers W to each of them.

Next, the structure of the resist coating unit 17 described above willbe explained in detail. FIG. 4 is an explanatory view of a verticalcross section showing a schematic structure of the resist coating unit17 and FIG. 5 is an explanatory view of a horizontal cross section ofthe resist coating unit 17.

In a center part of a casing 17 a of the resist coating unit 17, asshown in FIG. 4, a spin chuck 60 is provided with an upper surfacethereof formed to be flat and with a not-shown suction port formed in acenter part thereof so that the wafer W which is carried into the resistcoating unit 17 is horizontally held by suction onto the spin chuck 60.Under the spin chuck 60, a not-shown drive mechanism which causes thespin chuck 60 to be movable vertically and rotatable is disposed so thatthe wafer W can be rotated at a predetermined rotational speed when theresist solution is applied on the wafer W and the spin chuck 60 isvertically movable when the wafer W is mounted onto the spin chuck 60.

Around an outer circumference of the spin chuck 60, a circular cup 61with an upper part thereof being open is provided to surround the outercircumference of the spin chuck 60 so that the resist solution diffusedby a centrifugal force from the rotated wafer W which is held by suctiononto the spin chuck 60 is received therein and prevented fromcontaminating peripheral units. In a bottom portion of the cup 61, anot-shown drainpipe for draining out the resist solution which isspilled and diffused from the wafers W is formed.

A first exhaust pipe 62 for exhausting an atmosphere inside the cup 61is provided to extend from a bottom portion of the cup 61. The firstexhaust pipe 62 is communicated with a suction unit 63 via a secondexhaust pipe 83 as described later so that the atmosphere inside the cup61 can be actively exhausted by the suction unit 63. In the firstexhaust pipe 62, a first damper 64 serving as a first adjusting deviceis provided to adjust a flow rate of gas flowing through the firstexhaust pipe 62.

On a side in a negative direction of the X direction (a right directionin FIG. 4 and FIG. 5) of the cup 61, a case 66, which serves as anaccommodating portion, having a rectangular parallelepiped outer shapewhich is oblong in the Y direction (a vertical direction in FIG. 5) asshown in FIG. 5 is provided. Inside the case 66, provided is a nozzlecarrier 68, which serves as a carrier, for carrying a resist solutionsupply nozzle 67, which serves as a coating solution supply nozzle, fordischarging the resist solution onto the wafer W.

The nozzle carrier 68 includes a nozzle holding member 69 for holdingthe resist solution supply nozzle 67 to be suspended therefrom and anarm portion 70 to which the nozzle holding member 69 is fixed, as shownin FIG. 4. In the arm portion 70, a not-shown drive mechanism isprovided and the drive mechanism enables the arm portion 70 to movealong a rail 71 which extends in the Y direction as shown in FIG. 5 andto expand and contract in the Z direction. Therefore, the resistsolution supply nozzle 67 held by the nozzle holding member 69 ismovable in the Y and Z directions.

The nozzle holding member 69 is fixed in such a position that the nozzleholding member 69 is positioned above the center of the wafer W when thearm portion 70 moves to a position above the center of the wafer W sothat the resist solution is supplied to the center of the wafer W fromthe resist solution supply nozzle 67 which is held by the nozzle holdingmember 69.

In an upper surface of the case 66, a plurality of first ventilationholes 66 a are formed and a second ventilation hole 66 b is formed in alower part on a cup 61 side of the case 66 so that gas from the firstventilation holes 66 apasses through the case 66 and is discharged fromthe second ventilation hole 66 b to an area below the cup 61.

Outside the cup 61 on a positive direction side of the Y direction (theupward direction in FIG. 5), a nozzle box 72 for keeping theabove-mentioned resist solution supply nozzle 67 on stand-by therein isprovided. In the nozzle box 72, a plurality of recessed portions 73having the same outer shape as that of the resist solution supply nozzle67 are formed so that the resist solution supply nozzle 67 is allowed tobe received and kept on stand-by in the recessed portion 73. The nozzlebox 72 is structured to be movable in the X direction and the Xdirection movement of the nozzle box 72 causes a desired resist solutionsupply nozzle 67 to be positioned below the nozzle holding member 69which is fixed to the nozzle carrier 68 and enables the descendingnozzle holding member 69 to hold the resist solution supply nozzle 67.

A supply pipe 74, which serves as a supply device, for supplyingpredetermined gas, for example, air, which is the atmosphere, and inertgas, into the casing 17 a, is provided to extend from an upper surfaceof the casing 17 a. In the supply pipe 74, a damper 75 is attached toadjust a flow rate of the gas supplied into the casing 17 a to apredetermined flow rate. As the inert gas, for example, nitrogen gas,helium gas, and the like are usable.

On a downstream side of the damper 75 of the supply pipe 74, atemperature/humidity adjusting device 76 is disposed so that the gasflowing through the supply pipe 74 can be supplied into the casing 17 aafter being adjusted to appropriate temperature and humidity.

In an upper portion inside the casing 17 a, a flow dividing plate 77 fordividing the gas supplied from the supply pipe 74 is provided to beparallel to the upper surface of the casing 17 a. In the flow dividingplate 77, a number of ventilation holes 78 are formed as shown in FIG. 6and the ventilation holes 78 are more densely formed in an area facingthe cup 61, which is placed below the flow dividing plate, than in otherareas. This structure causes the gas supplied from the supply pipe 74 tobe divided by passing through each of the ventilation holes 78 so that astable descending air current is formed in the entire casing 17 a. Moreof the ventilation holes 78 are disposed in the area facing the cup 61to supply more gas into the cup 61.

At a position below the flow dividing plate 77 as high as the positionof the cup 61, a current plate 80 is disposed horizontally to surroundthe outer circumference of the cup 61. In the current plate 80, a numberof holes 81 are formed as shown in FIG. 5 and the gas after passingthrough the flow dividing plate 77 passes through the holes 81 so that alinear descending air current is formed from the flow dividing plate 77to the current plate 80.

A second exhaust pipe 83, which serves as a second exhaust pipe, with anexhaust port 82 thereof facing upward is provided to extend from aninner bottom portion of the casing 17 a so that an atmosphere inside thecasing 17 acan be actively exhausted by the suction unit 63. In thesecond exhaust pipe 83, a second damper 84, which serves as a secondadjusting device, for adjusting a flow rate of the atmosphere flowingthrough the second exhaust pipe 83 is attached. A downstream side of thefirst exhaust pipe 62 which extends from the cup 61 is communicated withthe second exhaust pipe 83 on an upstream side of the second damper 84and the atmosphere inside the cup 61 is also exhausted through thesecond exhaust pipe 83 in the end. As described above, the gas from thefirst exhaust pipe 62 is confluent with the second exhaust pipe 83 butthe exhaust flow rate of the first exhaust pipe 62 is adjusted by thefirst damper 64 which is provided on the upstream side so that thesecond damper 84 adjusts only the flow rate of the atmosphere inside thecasing 17 a which is exhausted from the exhaust port 82.

The first damper 64 in the first exhaust pipe 62, the damper 75 in thesupply pipe 74, and the second damper 84 in the second exhaust pipe 83described above are controlled by a controller 85 and the controller 85enables the flow rates of the air currents flowing through the firstexhaust pipe 62, the second exhaust pipe 83, and the supply pipe 74 tobe maintained at predetermined flow rates and the flow rates to bechanged to predetermined flow rates at predetermined timing.

Next, the operation of the resist coating unit 17 as structured above isexplained together with the steps of a photolithography processperformed in the coating and developing treatment system 1.

First, the wafer carrier 7 takes out one unprocessed wafer W from thecassette C and carries it to the adhesion unit 31 which is included inthe third processing unit group G3. The wafer W, which is coated with anadhesion promoter such as HMDS for improving fixability with the resistsolution in the adhesion unit 31, is carried to the cooling unit 30 bythe main carrier 13 and cooled to predetermined temperature. Thereafter,the wafer W is carried to the resist coating unit 17 or 19.

The wafer W with the resist film formed thereon is carried again to thepre-baking unit 33 or 34 and the extension and cooling unit 41 insequence by the main carrier 13 to undergo predetermined processing.

Then, the wafer W is taken out from the extension and cooling unit 41 bythe wafer carrier 50 and carried to the aligner (not-shown) via theperipheral aligner 51. The wafer W after undergoing the exposureprocessing is carried to the extension unit 42 by the wafer carrier 50and further carried to the post-exposure baking unit 44 or 45, thedeveloping unit 18 or 20, the post-baking unit 35, 36, 46, or 47, andthe cooling unit 30 in sequence by the main carrier 13 to undergopredetermined processing in each of the units. Thereafter, the wafer Wis returned to the cassette C by the wafer carrier 7 via the extensionunit 32 and a series of predetermined coating and developing treatmentis finished.

Next, the operation of the resist coating unit 17 described above willbe explained in detail. First, the supply of the air whose temperatureand humidity is adjusted is started into the casing 17 a from the supplypipe 74 before the wafer W is carried to the resist coating unit 17. Theflow rate of the supplied air at this time is adjusted to, for example,2.1 m³/min. by the controller 85 and the damper 75 so that the speed ofthe air flowing through the supply pipe 74 is, for example, made to beapproximately 0.3 m/s.

Synchronously with this operation, the suction unit 63 starts to operateso that the atmosphere inside the cup 61 is exhausted from the firstexhaust pipe 62 and the atmosphere inside the casing 17 a starts to beexhausted from the exhaust port 82. At this time, the flow rate insidethe first exhaust pipe 62 is adjusted to, for example, 1.5 m³/min.,which is a first flow rate, and the flow rate inside the second exhaustpipe 83 is adjusted to, for example, 2.0 m³/min, which is a second flowrate.

As a result, the air of 2.1 m³/min. which is supplied from the supplypipe 74 passes through the flow dividing plate 77 to be supplied intothe entire casing 17 a, and the air of 1.5 m³/min. out of the suppliedair flows into the cup 61 and is exhausted from the first exhaust pipe62 while purging the inside of the cup 61. Meanwhile, the air of 0.5m³/min. (a difference between the first flow rate and the second flowrate) out of the supplied air passes through the current plate 80 or thecase 66 and is exhausted from the exhaust port 82 through the secondexhaust pipe 83 while forming the descending air current inside thecasing 17 a. The remaining air of 0.1 m³/min. serves for maintaining thepressure inside the casing 17 a at the positive pressure.

As described above, the resist coating treatment for the wafer W isstarted after the atmospheres inside the casing 17 a and the cup 61 aremaintained in appropriate conditions. First, the wafer W is carried intothe resist coating unit 17 by the main carrier 13, delivered to the spinchuck 60 which is ascended and kept on stand-by in advance, andthereafter held by suction onto the spin chuck 60. Then, the spin chuck60 is descended to place the wafer W in a predetermined position insidethe cup 61.

When the wafer W is placed in the predetermined position inside the cup61, the nozzle carrier 68 moves in the Y direction to hold the resistsolution supply nozzle 67 which is kept on stand-by in the nozzle box72. Then, it moves in the Y direction again to transfer the resistsolution supply nozzle 67 to a position above the center of the wafer W.Next, the rotation of the wafer W is started at a predeterminedrotational speed, for example, at 100 rpm, by the spin chuck 60. At thistime, the exhaust flow rate in the first exhaust pipe 62 is increased,for example, from 1.5 m³/min. to 2.0 m³/min. by the first damper 64.

After that, the resist solution is discharged from the resist solutionsupply nozzle 67 and a predetermined amount of the resist solution issupplied onto the center of the wafer W. Then, the rotational speed ofthe wafer W is increased to, for example, 4,000 rpm, after thepredetermined amount of the resist solution is supplied so that theresist solution on the wafer W is diffused onto the entire surface ofthe wafer W to form the resist film. Thereafter, the rotational speed ofthe wafer W is reduced to, for example, 2,500 rpm and the resistsolution is further diffused to make the resist film thin. Then, whenthe resist film with a predetermined film thickness is formed, therotation of the wafer W is stopped. At this time, the exhaust flow rateinside the first exhaust pipe 62 is decreased from 2.0 m³/min. to 1.5m³/min.

When the predetermined resist film is thus formed on the wafer W and therotation of the wafer W is stopped, the resist solution supply nozzle 67is transferred again to the nozzle box 73 to be returned to the recessedportion 74 of the nozzle box 73. Meanwhile, the wafer W on which theresist film is formed is ascended by the spin chuck 60 again anddelivered to the main carrier 13 from the spin chuck 60. Then, theresist coating treatment is finished when the wafer W is carried fromthe resist coating unit 17 to the pre-baking unit 33 where thesubsequent process is carried out.

According to the above embodiment, the second exhaust pipe 83 forexhausting the atmosphere inside the casing 17 a and the first exhaustpipe 62 for exhausting the atmosphere inside the cup 61 are separatelyprovided so that the pressure inside the casing 17 a can be adjusted tothe positive pressure with the use of only the second exhaust pipe 83.Therefore, the first exhaust pipe 62 does not need to be burdened withboth of the works of exhausting the atmosphere inside the cup 61 andperforming the positive pressure adjustment, as is conventionallyrequired, so that the atmospheres inside the casing 17 aand the cup 61can easily be adjusted.

The first exhaust pipe 62 is provided to be connected to the secondexhaust pipe 83 so that the atmospheres inside the cup 61 and the casing17 acan finally be exhausted from one exhaust pipe, and thereby only onepiping system is required for exhausting the atmospheres.

The current plate 80 is provided around the cup 61 so that thedescending air current inside the casing 17 a which is formed byproviding the second exhaust pipe 82 is uniformly formed inside thecasing 17 a. This enables impurities inside the casing 17 a to beappropriately discharged.

Furthermore, the exhaust flow rate inside the cup 61 is increased onlywhen the resist solution is supplied onto the rotated wafer W and theresist solution is diffused so that mist, which is produced from theresist solution in a large amount at the above timing, is prevented fromflowing out of the cup 61 into the casing 17 a.

According to the above embodiment, the first exhaust pipe 62 is providedto be connected to the second exhaust pipe 83 as described above but thefirst exhaust pipe 62 and the second exhaust pipe 83 may be providedindependently without being connected to each other. In this case, thepressure inside the casing 17 a and the exhaust flow rate inside the cup61 can also be adjusted by different exhaust pipes, which makes itpossible to facilitate the atmosphere control while the resist treatmentis carried out, compared with a conventional art.

According to the above embodiment, the atmosphere inside the case 66 ofthe nozzle carrier 68 is exhausted by the second exhaust pipe 83similarly to the atmosphere inside the casing 17 a but an exhaust pipefor exhausting the atmosphere inside the case 66 may separately beprovided.

In this case, for example, as shown in FIG. 7, it is proposed that anexhaust pipe 90 serving as a third exhaust pipe is provided to extendfrom a lower part of a side surface of the case 66 so that theatmosphere inside the case 66 can actively be exhausted, for example, bythe suction unit 63. When the wafer W undergoes the resist coatingtreatment, the atmosphere inside the case 66 needs to be constantlyexhausted and purged. Thereby, a clean atmosphere can be maintainedaround the nozzle carrier 68 which includes many drive mechanisms and inwhich impurities are easily produced and the impurities are preventedfrom adhering to the wafer W inside the cup 61.

The atmosphere inside the case 66 may constantly be exhausted while theresist coating treatment is performed, as described above, but may beexhausted only when the resist solution supply nozzle 67 which is heldby the nozzle carrier 68 is placed above the wafer W. In other words,the atmosphere inside the case 66 is exhausted only when the impuritiesproduced in the nozzle carrier 68 tend to easily drop onto the wafer W.Thereby, the atmosphere is prevented from being exhausted unnecessarilyand excessively to stabilize the air current inside the casing 17 a andreduce power consumption which is required for exhausting.

According to the above embodiment, the coating unit applies the resistsolution on the wafer W to form the resist film but the presentinvention is applicable to a coating unit for applying a coatingsolution other than the resist solution, for example, a developingsolution. It is also applicable to a coating unit for substrates otherthan the wafer W, for example, an LCD substrate.

According to the present invention, different pipes are usable forexhausting the atmosphere inside the casing to maintain the pressureinside the casing at the positive pressure and exhausting the atmosphereinside the cup to prevent the atmosphere inside the cup from flowingout, which makes it possible to realize easier atmosphere controlsatisfying a plurality of conditions.

Moreover, according to the present invention, the atmospheres inside thecasing and the cup can be exhausted only with one piping system so thata piping facility thereof is simplified and unnecessary facilities canbe omitted to realize cost reduction.

What is claimed is:
 1. A coating unit for applying a coating solution ona substrate, comprising: a container enclosing the substrate; a casingfor accommodating said container therein; a supply device for supplyinga predetermined gas into said casing; a first exhaust pipe forexhausting an atmosphere inside said container; a second exhaust pipefor exhausting an atmosphere inside said casing; a first adjustingdevice which is disposed in said first exhaust pipe, for adjusting aflow rate of an atmosphere passing through said first exhaust pipe; anda second adjusting device which is disposed in said second exhaust pipe,for adjusting a flow rate of an atmosphere passing through said secondexhaust pipe, wherein a downstream side of said first exhaust pipe isconnected to an upstream side of said second adjusting device in saidsecond exhaust pipe.
 2. A coating unit according to claim 1, wherein thegas is supplied from a top portion of said casing in a downwarddirection by said supply device, and wherein said second exhaust pipe isdisposed to extend from a bottom portion of said casing.
 3. A coatingunit according to claim 2, further comprising: a current plate forstraightening a descending air current caused to occur inside saidcasing by said supply device and said second exhaust pipe.
 4. A coatingunit according to claim 3, further comprising: a carrier for carrying acoating solution supply nozzle for supplying the coating solution to thesubstrate which is placed inside said container; an accommodatingportion for accommodating said carrier which is disposed inside saidcasing; and a third exhaust pipe for exhausting an atmosphere insidesaid accommodating portion.
 5. A coating unit for applying a coatingsolution on a substrate, comprising: a container enclosing thesubstrate; a casing for accommodating said container therein; a supplydevice for supplying a predetermined gas into said casing; a firstexhaust pipe for exhausting an atmosphere inside said container; asecond exhaust pipe for exhausting an atmosphere inside said casing; afirst adjusting device which is disposed in said first exhaust pipe, foradjusting a flow rate of an atmosphere passing through said firstexhaust pipe; a second adjusting device which is disposed in said secondexhaust pipe, for adjusting a flow rate of an atmosphere passing throughsaid second exhaust pipe; a carrier for carrying a coating solutionsupply nozzle for supplying the coating solution to the substrate whichis placed inside said container; an accommodating portion foraccommodating said carrier which is disposed inside said casing; and athird exhaust pipe for exhausting an atmosphere inside saidaccommodating portion.
 6. A coating unit according to claim 5, whereinthe gas is supplied from a top portion of said casing in a downwarddirection by said supply device, and wherein said second exhaust pipe isdisposed to extend from a bottom portion of said casing.
 7. A coatingunit according to claim 5, further comprising: a current plate forstraightening a descending air current caused to occur inside saidcasing by said supply device and said second exhaust pipe.
 8. A coatingunit for applying a coating solution on a substrate, comprising: acontainer enclosing the substrate; a casing for accommodating saidcontainer therein; a supply device for supplying a predetermined gasinto said casing; a first exhaust pipe for exhausting an atmosphereinside said container; a second exhaust pipe for exhausting anatmosphere inside said casing; a first adjusting device which isdisposed in said first exhaust pipe, for adjusting a flow rate of anatmosphere passing through said first exhaust pipe; a second adjustingdevice which is disposed in said second exhaust pipe, for adjusting aflow rate of an atmosphere passing through said second exhaust pipe, acarrier for carrying a coating solution supply nozzle for supplying thecoating solution to the substrate which is placed inside said container;an accommodating portion for accommodating said carrier which isdisposed inside said casing; and a third exhaust pipe for exhausting anatmosphere inside said accommodating portion, wherein a downstream sideof said first exhaust pipe is connected to an upstream side of saidsecond adjusting device in said second exhaust pipe.
 9. A coating unitfor applying a coating solution on a substrate, comprising: a containerenclosing the substrate; a casing for accommodating said containertherein; a supply device for supplying a predetermined gas into saidcasing; a first exhaust pipe for exhausting an atmosphere inside saidcontainer; a second exhaust pipe for exhausting an atmosphere insidesaid casing; a first adjusting device which is disposed in said firstexhaust pipe, for adjusting a flow rate of an atmosphere passing throughsaid first exhaust pipe; a second adjusting device which is disposed insaid second exhaust pipe, for adjusting a flow rate of an atmospherepassing through said second exhaust pipe; a current plate forstraightening a descending air current caused to occur inside saidcasing by said supply device and said second exhaust pipe; a carrier forcarrying a coating solution supply nozzle for supplying the coatingsolution to the substrate which is placed inside said container; anaccommodating portion for accommodating said carrier which is disposedinside said casing; and a third exhaust pipe for exhausting anatmosphere inside said accommodating portion, wherein the gas issupplied from a top portion of said casing in a downward direction bysaid supply device, and wherein said second exhaust pipe is disposed toextend from a bottom portion of said casing.